High impedance, high frequency slip ring



Dec. 14, 1965 c. J. LAPHAM HIGH IMPEDANCE, HIGH FREQUENCY SLIP RING Filed June 18, 1964 INVENTOR Charles J. Lopham ATTORNEYS United States Patent 3,223,949 HIGH IMPEDANCE, HIGH FREQUENCY SLIP RING Charles J. Lapham, Lincoln Park, N.J., assignor to Electro- Tec Corp., West Caldwell, N.J., a corporation of New Jersey Filed June 18, 1964, Ser. No. 376,198 9 Claims.. (Cl. 33324) This application is a continuation-in-part of my copending application Serial Number 332,576, filed December 23, 1963, now abandoned.

This invention relates to current collector means and more particularly, to rotary slip ring means for use with high frequency alternating currents.

It is an object of this invention to provide a rotary slip ring structure which is particularly well adapted for use with high frequency alternating currents having their frequency rates in the radio-frequency (RF) range.

Another object of this invention is to provide a rotary slip ring structure which presents a high characteristic impedance to an RF signal fed at a plurality of points.

Still another object of this invention is to provide a rotary slip ring structure which presents a higher characteristic impedance to RF signals in shorter axial lengths thereby permitting fabrication of such slip ring structure in smaller shapes than has been heretofore possible without increasing the voltage standing wave ratio.

Yet another object of this invention is to provide a rotary slip ring structure wherein the change of input impedance thereof, with rotation, is minimized.

Another object of this invention is to provide a slip ring accomplishing the above objects which may be either parallel fed or single fed as required. The single fed embodiment is shown in parent application Serial Number, 332,576, now abandoned.

These and other objects of this invention will become more fully apparent with reference to the following specification and drawings which relate to a preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a side elevation of a slip ring of the present invention in partial cross-section; and FIGURE 2 is a cross-section taken along line 22 of FIGURE 1.

Referring in detail to the drawings, and more particularly to FIGURES 1 and 2, a preferred embodiment of the slip-ring'assembly 10 of the present invention is shown as including an outer, cylindrical, concentric housing means 12 having symmetrically disposed first and second peripheral. openings 14A and 14B therein which are adapted to receive, respectively, first and second coaxial terminal connections 16A and 16B.

Internally concentric with the housing means 12 is a conductive ring member 18 comprising first and second juxtaposed portions 20 and 22, respectively which provide a peripheral channel 24 therebetween on the ring member. 18'.

The ring member 18 comprises the outer conductor means of the slip ring assembly 10 which, as will be hereinafter described either feeds or is fed by the coaxial terminal connection 16. An axial bore 26 is provided in the conductive ring member 18.

The inner conductor means of the slip ring assembly 10 generally comprises a supporting ring 28 having at least an insulating peripheral surface, a toroidal winding 30 thereon in insulated relation thereto and a plurality of contact elements, shown as conductive segments 32, concentrically disposed about the supporting ring 28.

The supporting ring 28 and the toroidal winding 30 are embedded in potting compound or other suitable insulation 34 adjacent to the inner end wall 36 of the channel 24,v said end wall being integral with the first juxtaposed portion 20 of the conductive ring 18. Thus, the toroidal winding 30 is electrically isolated from the conductive ring 18.

The conductive segments 32 are separated from the toroidal winding 30 by means of a layer of the insulating material 34 in the channel 24.

The toroidal winding 30 is a continuous closed spiral with each turn thereof connected to one of the conductive segments 32 by means of coupling spikes 38 which extend from the inner surface of the segments 32 to pierce the insulation on the toroidal winding 30 and make contact with the conductor thereof.

The toroidal winding 30 is joined at first and second diametrically opposed points 39A and 39B with the respective inner conductors of first and second coaxial cables 40A and 40B. The said first and second coaxial cables 40A and 40B include, respectively, first and second outer conductors 42A and 42B connected to the conductive outer ring 18 at solder points 44A' and 44B, respectively, or the like.

The coaxial cables 40A and 40B are adapted to be connected to the respective winding-s of a rotor, not shown, with which the slip ring assembly 10 is rotatable, the axis of the bore 26 of the ring assembly coinciding with the axis of the rotor.

Current is transmitted between the conductive ring 18 and the external or outer conductors of the coaxial terminals 16A and 16B via first spring type brush sets 46A and 46B, respectively, including oppositely extending spring arms 48A and 50A and 48B and 503. The spring arms 48A and 50A have a common hub portion 52A and carry, respectively, first and second contact brushes 54A and 56A. The spring arms 48B and 50B have a common hub portion 52B and carry, respectively, first and second contact brushes 54B and 56B.

The brushes 54A-56A and 54B-56B slidably engage the peripheral surface 58 of the second portion 22 of the conductive ring 18.

The common hub portions 52A and 52B of the first brush sets 46A and 46B are respectively secured to the first and second coaxial terminals 16A and 163 via pairs of set screws 60A and 6013.

The central or internal conductors of the coaxial terminals 16A and 16B comprises, respectively, conductive dependent stud-s 62A and 62B which, in the channel 24 of the conductive ring 18 centrally support second brush sets 64A and 64B, respectively.

The brush set 64A includes oppositely extending spring arms 66A and 68A which carry, respectively, third and fourth contact brushes 70A and 72A on their outer ends, slidably engaged with the contact strips 32.

The brush set 64B includes oppositely extending spring arms 66B and 68B which carry, respectively, third and fourth contact brushes 70B and 72B on their outer ends, slidably engaged with the contact strips 32 at diametri cally opposed points with respect to the contact brushes 70A and 72A, respectively. Thus, complete symmetry is maintained in the geometry of the slip ring assembly 10.

Isolating slots 74 are provided by any suitable means in the insulating material 34 between adjacent conductive contact strips 32, whereby during substantially the entire time the slip ring assembly 10 is rotating, the third and fourth contact brushes 70A-72A and 76B72B of the respective second brush sets 64A and 64B are each in contact with diiferent adjacent ones of the conductive strips 32.

The conductive strips 32 and the brush sets 64A and 64B are so proportioned as to always be electrically isolated from the conductive ring 18.

In operation, assuming electric signals are being introduced into a rotor, in parallel through the coaxial terminals 16A and 16B of the slip ring assembly 10, and further assuming rotation of the conductive ring 18, the outer conductors of the said terminals 16A and 16B carrying the coaxially transmitted signals are connected to the conductive ring 18 via the first brush sets 46A and 46B, respectively, and thus, to the outer conductors 42A and 42B of the internal coaxial leads 40A and 40B. Simultaneously, the inner conductors of the terminals 16A and 16B carrying the coaxially transmitted signals are connected to the toroidal inner winding 30 and the respective inner conductors of the internal coaxial leads 40A and 40B via the studs 62A and 62B, the second brush sets 64A and 64B, the respectively engaged conductive segments 32, contact spikes 38 and the connection points 39A and 39B, respectively.

The toroidal winding 30 is selected as to the number of turns therein and its dimensions to provide an impedance match between the circuits feeding the signals to the coaxial input terminals 16A and 16B and the circuits fed by the brush sets 60A, 60B, 62A and 62B, thereby overcoming one of the major characteristics of prior art slip rings found to be objectionable at higher frequencies, namely, the characteristic of low impedance.

Thus, for example, it is possible to feed video frequency signals in parallel through the same slip ring; to feed IF (intermediate frequency) signals in parallel through the same slip ring; or, with suitable filters to provide selective output coupling, to feed IF signals and video frequency signals in parallel through the same slip ring.

Further, the geometry of the present invention provides a parallel fed high frequency slip ring in which variations in both the impedance and voltage standing wave ratio, during rotation, are minimized.

As can be readily seen from the foregoing specification and drawings, the present invention satisfies a long felt need in the art for a parallel fed, high frequency slip ring which provides a matched impedance coupling between the respective input and output circuits associated therewith.

It is to be understood that the particular embodiment shown and described herein is for the sake of example only and is not intended to limit the scope of the appended claims. For example, a single input terminal may be used as disclosed in aforesaid parent application, Serial Number 332,576, other arrangements and numbers of input terminals, brushes and other structural components are within the skill of an ordinary mechanic in the art and are within the spirit of this invention as defined by the following claim.

What is claimed is:

1. A slip ring assembly for multiconductor signal transmission comprising a transmission terminal, a rotary conductive ring means adjacent said terminal, a peripheral channel formed in said ring means, second conductive means coterminate with said peripheral channel adjacent the inner wall thereof, insulating means in said channel isolating said second conductive means from said conductive ring means, first and second contact means extending between said transmission terminal and said conductive ring means and second conductive means, respectively, and transmission means comprising multiconductor means having as one of its conductors an extension of said second conductive means and having another of its conductors electrically connected with said conductive ring means, second conductive means comprising a toroidal winding and a plurality of contact elements mutually isolated from each other, selectively connected with particular convolutions of said toroidal Winding and peripherally disposed with respect to said winding.

2. The invention defined in claim 1, wherein said second conductive means comprises an annular core, the toroidal winding being on said core and the plurality of contact elements being conductive segments, and wherein said second contact means comprises a plurality of brush means contacting a plurality of said conductive segments.

3. In a slip ring assembly, an annular channel shaped rotary conductor, insulating means partially filling the said annular channel shaped conductor, annular core means embedded in said insulating means, a conductive toroidal winding on said core means, and a plurality of conductive segments, peripherally disposed about said toroidal Winding separated therefrom by said insulating means, selectively and respectively electrically connected with selected convolutions of said toroidal winding.

4. The invention defined in claim 3, wherein said conductive segments are maintained in mutual isolation by a plurality of radial slots in said insulating means.

5. A parallel fed slip ring assembly for multiconductor signal transmission between first and second circuit means comprising a rotary conductive ring means, equally spaced transmission terminals adjacent said conductive ring means, a peripheral channel formed in said ring means, second conductive means coterminate with said peripheral channel adjacent the inner wall thereof, insulating means in said channel isolating said second conductive means from said conductive ring means, first and second contact means extending between each of said transmission terminals and said conductive ring means and second conductive means, respectively, and equally spaced transmission means corresponding in number to and associated one with each of said transmission terminals, each of said second transmission means comprising multiconductor means having one of its conductors electrically connected with said second conductive means and having another of its conductors electrically connected with said conductive ring means, said second conducting means comprising impedance matching means for said first and second circuit means.

6. The invention defined in claim 5, wherein said second conductive means includes a toroidal winding and a plurality of contact elements, mutually isolated from each other, selectively connected with particular convolu tions of said toroidal winding and peripherally disposed with respect to said winding.

7. The invention defined in claim 6, wherein said first and second contact means comprise a plurality of equally spaced brush means in contact with said conductive ring means and with said conductive segments, respectively.

8. The invention defined in claim 6, wherein said toroidal winding is on an annular core and a plurality of conductive segments, mutually isolated from each other, selectively connected with particular convolutions of said toroidal winding and peripherally disposed with respect to said core. I

9. The invention defined in claim 5, wherein said second conductive means includes an annular core, a toroidal winding on said core and a plurality of conductive segments, mutually isolated from each other, selectively connected with particular convolutions of said toroidal winding and peripherally disposed with respect to said core; and wherein said first and second contact means comprise a plurality of equally spaced brush means in contact with said conductive ring means and with said conductive segments, respectively.

HERMAN KARL SAALBACH, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,223,949 December 14, 1965 Charles J. Lapham It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant (only), line 1, for "Charles J. Japham" read Charles J. Lapham column 3, line 52, for "claim" read claims Signed and sealed this 18th day of October 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

3. IN A SLIP RING ASSEMBLY, AN ANNULAR CHANNEL SHAPED ROTARY CONDUCTOR, INSULATING MEANS PARTIALLY FILLING THE SAID ANNULAR CHANNEL SHAPED CONDUCTOR, ANNULAR CORE MEANS EMBEDDED IN SAID INSULATING MEANS, A CONDUCTIVE TOROIDAL WINDING ON SAID CORE MEANS, AND A PLURALITY OF CONDUCTIVE SEGMENTS, PERIPHERALLY DISPOSED ABOUT SAID TOROIDAL WINDING SEPARATED THEREFROM BY SAID INSULATING MEANS, SELECTIVELY AND RESPECTIVELY ELECTRICALLY CONNECTED WITH SELECTED CONVOLUTIONS OF SAID TOROIDAL WINDING. 